Average width of a line is determined by _both_ junctions.
Average width of a line is determined by _both_ junctions.

Don't only use one junction to determine the width of the line, the width of a line is (approximately) the average of both its junctions.

part of CURA-9036

Co-authored-by: Ghostkeeper <73dd685754fb6b1f449135334f692e6f8d8a3068@tutanota.com>

Ultimaker/CuraEngine,Ultimaker/CuraEngine